I feel like I'm losing my mind there, a lot of people struggling to comprehend a diet where "protein" isn't a category, made from animals or plants otherwise.
Btw Impossible burger etc. are not vegan, they do animal testing: https://impossiblefoods.com/blog/the-agonizing-dilemma-of-animal-testing
CW animal testing
But we were confronted with an agonizing dilemma: We knew from our research that heme is absolutely essential to the sensory experience meat lovers crave. Replacing animals in the diets of meat lovers would absolutely require heme. So without the rat testing, our mission and the future of billions of animals whose future depends on its success was thwarted. We chose the least objectionable of the two choices available to us. We used the minimum number of rats necessary for statistically valid results.
Yay capitalism lets us have our treats, and only a few animals had to suffer! 
Lentil soup and a falafel sandwich from an Arabic market blow any impossible bullshit out of the water. I just wish I could make it that good myself.
You can! Practice making lentils and chickpeas for 15 minutes a day for a few years!